Wireless communication system, communication apparatus, and communication method

ABSTRACT

A wireless communication system includes a first antenna, a second antenna with an orientation relative to the first antenna that is changeable around a predetermined axis, and a communication control unit that controls wireless communication based on electric field coupling between the first antenna and the second antenna. The first antenna includes a first electrode including a bored portion, where the predetermined axis passes through an inside of the bored portion. The first antenna also includes a second electrode located inside the bored portion The second antenna includes a third electrode that transmits an electric signal between the first electrode and the third electrode and a fourth electrode that transmits an electric signal between the second electrode and the fourth electrode.

BACKGROUND

Field

The present disclosure relates to a wireless communication system.

Description of the Related Art

In recent years, there has been a system carrying out communication viaa rotatable portion, such as an articulation portion of a robot arm, anda joint portion between a network camera and a camera platform. Therehas also been a system carrying out communication between twoapparatuses connectable to each other in a plurality of differentorientations, such as a communication cable for a mobile devicesupporting reversed insertion. When wireless communication is used forthe communication in a system like such systems, an orientation of areception antenna is changeable relative to a transmission antenna.

Japanese Patent Application Laid-Open No. 2016-29785 discusses a methodfor realizing high-quality communication by carrying out communicationbased on electromagnetic field using a transmission antenna and areception antenna, each including two electrodes. More specifically,Japanese Patent Application Laid-Open No. 2016-29785 discusses a methodfor transmitting data by inputting a differential signal that is anelectric signal of opposite phase into a first transmission electrodeand a second transmission electrode included in the transmissionantenna.

The communication can, however, be destabilized in a system carrying outthe wireless communication between one antenna including a plurality ofelectrodes and another antenna including a changeable orientationrelative to the antenna. For example, it is conceivable that efficiencyof the communication is substantially changed according to theorientation of the antenna in a case where the electrode included in theone antenna and the electrode included in the other antenna face eachother in some orientation, but do not face each other in a differentorientation.

SUMMARY

According to an aspect of the present disclosure, a wirelesscommunication system includes a first antenna, a second antennaincluding an orientation relative to the first antenna that ischangeable around a predetermined axis, and a communication control unitconfigured to control wireless communication based on electric fieldcoupling between the first antenna and the second antenna. The firstantenna includes a first electrode including a bored portion, which isconfigured such that the predetermined axis passes through the inside ofthe bored portion, and a second electrode located inside the boredportion as viewed from a reference direction that is in parallel withthe predetermined axis. The second antenna includes a third electrodeconfigured such that an electric signal is transmitted between the firstelectrode and the third electrode, and a fourth electrode configuredsuch that an electric signal is transmitted between the second electrodeand the fourth electrode.

Further features will become apparent from the following description ofexemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system configuration of a wireless communicationsystem.

FIGS. 2A to 2C illustrate electric signals input and output in thewireless communication system.

FIG. 3 illustrates an example in which the wireless communication systemis applied to a network camera.

FIGS. 4A to 4D illustrate examples of a shape of a coupler.

FIG. 5 illustrates a configuration of a wireless communication systemcarrying out wireless power transmission.

FIG. 6 illustrates a configuration of a connection portion in thewireless communication system carrying out the wireless powertransmission.

FIGS. 7A to 7D illustrate examples of a shape of a coupler having aslit.

FIG. 8 illustrates a configuration of a wireless communication systemincluding a balun.

FIG. 9 illustrates an example of a case where the shapes of the couplersare different from each other.

DESCRIPTION OF THE EMBODIMENTS

[System Configuration]

FIG. 1 illustrates a schematic configuration of a wireless communicationsystem 100 (hereinafter referred to as a system 100) according to anexemplary embodiment. The system 100 includes a signal source 101, asignal line 102-1, a signal line 102-2, a coupler 103, a coupler 104, asignal line 105-1, a signal line 105-2, and a waveform shaping device106 (hereinafter referred to as a shaper 106). In the present exemplaryembodiment, the signal line 102-1 and the signal line 102-2 will besimply referred to as a signal line 102 when there is no need todistinguish them from each other. Similarly, the signal line 105-1 andthe signal line 105-2 will be simply referred to as a signal line 105when there is no need to distinguish them from each other.

The coupler 103 and the coupler 104 are each a conductor functioning asan antenna for carrying out wireless communication based onelectromagnetic field coupling, and each include two electrodes, i.e.,an inner electrode and an outer electrode. An electric signal istransmitted between the outer electrode of the coupler 103 and the outerelectrode of the coupler 104, and an electric signal is transmittedbetween the inner electrode of the coupler 103 and the inner electrodeof the coupler 104. Specifically, the coupler 103 and the coupler 104are each configured such that a copper pattern serving as the electrodeis formed on a printed circuit board, such as Flame Retardant Type 4(FR4) or flexible printed circuits. However, the configurations of thecoupler 103 and the coupler 104 are not limited thereto. Theelectromagnetic field coupling according to the present exemplaryembodiment includes both electric field coupling (capacitive coupling)and magnetic field coupling. In other words, the wireless communicationbetween the coupler 103 and coupler 104 can be carried out based on theelectric field coupling or can be carried out based on the magneticfield coupling. In the present exemplary embodiment, the system 100 willbe described, focusing mainly on a case in which the communication iscarried out between the coupler 103 and the coupler 104 based on theelectric field coupling.

The signal source 101 generates a differential signal and inputs thedifferential signal to the signal line 102. More specifically, electricsignals of opposite phase to each other are input to the signal line102-1 and the signal line 102-2, respectively. The signal line 102-1 isconnected to one of the two electrodes included in the coupler 103 andthe signal line 102-2 is connected to the other electrode, and thedifferential signal generated by the signal source 101 is input to thecoupler 103 via the signal line 102. In other words, the electricsignals of the opposite phase to each other are input to the twoelectrodes included in the coupler 103 by the signal source 101.

When the differential signal is input to the coupler 103, a voltage isgenerated in the coupler 104 based on this input. In other words, anelectric signal transmitted from the coupler 103 is received by thecoupler 104. The signal line 105-1 is connected to one of the twoelectrodes included in the coupler 104 and the signal line 105-2 isconnected to the other electrode, and the differential signal receivedby the coupler 104 is transmitted to the shaper 106 via the signal line105. More specifically, an electric signal received by the outerelectrode of the coupler 104 based on the signal input to the outerelectrode of the coupler 103, and an electric signal received by theinner electrode of the coupler 104 based on the signal input to theinner electrode of the coupler 103 are input to the shaper 106.

The shaper 106 then generates an electric signal including a form closerto a waveform of the signal output from the signal source 101 based onthe electric signals received by the two electrodes. The shaper 106outputs the generated electric signal to, for example, a functional unit(not illustrated) included in the system 100. The not-illustratedfunctional unit include a display control unit that displays an imagebased on the input electric signal on a display unit, and a transferunit that transfers data based on the input electric signal to anexternal apparatus. In this manner, the system 100 controls the wirelesscommunication between the coupler 103 and the coupler 104 using thesignal source 101 and the shaper 106.

FIGS. 2A to 2C illustrate examples of waveforms of the electric signalsinput and output in the system 100. A horizontal axis in each of FIGS.2A to 2C indicates time. First, a transmission signal illustrated inFIG. 2A generated by the signal source 101 is input to the coupler 103via the signal line 102-1. The coupler 104 is coupled with the coupler103 by the electric field coupling, so that a reception signalillustrated in FIG. 2B is generated at the coupler 104 based on thetransmission signal input to the coupler 103. This reception signalincludes a differentiated waveform of the signal input to the coupler103. Then, the reception signal illustrated in FIG. 2B is input to theshaper 106 via the signal line 105-1.

The signal source 101 inputs a signal of the opposite phase to thetransmission signal illustrated in FIG. 2A into the coupler 103 via thesignal line 102-2. A signal of the opposite phase to the receptionsignal illustrated in FIG. 2B is generated at the coupler 104 accordingto this input, and the generated signal is input to the shaper 106 viathe signal line 105-2.

The shaper 106 performs shaping processing on the differential signalinput via the signal line 105, and generates a shaped signal illustratedin FIG. 2C that includes a waveform similar to the transmission signaloutput from the signal source 101. By the above-described process,wireless transmission of digital data is realized. In the presentexample, the transmitted electric signal is assumed to be a binarydigital signal, but is not limited thereto and can be a multivaluedsignal.

In the present exemplary embodiment, the system 100 is describedreferring to an example in which the communication is carried out bybaseband transmission that is not accompanied by modulation anddemodulation of a carrier wave. However, the exemplary embodiment is notlimited thereto. The exemplary embodiment can be carried out byinputting a carrier wave modulated based on the signal output from thesignal source 101 to the coupler 103, and demodulating the signal outputfrom the coupler 104.

[Example of Application to Network Camera]

An example of a case where the system 100 is applied to transmission ofimaging data in a network camera 300 will be described with reference toFIG. 3. The network camera 300 includes an imaging unit 302 and a cameraplatform 303, and the imaging unit 302 and the camera platform 303 areattachable to and detachable from each other at a connection portion 304that is a boundary therebetween. The camera platform 303 is fixed to aninstallation location, such as a ceiling and a wall. When the networkcamera 300 is configured in this manner, the imaging unit 302 can easilybe replaced when replacement of the imaging unit 302 becomes necessarydue to a failure or the like.

In the network camera 300, the coupler 103 is included in the imagingunit 302 and the coupler 104 is included in the camera platform 303.Image data based on imaging by an imaging control unit 305 istransmitted from the coupler 103 to the coupler 104, and is transmittedto an external network via the shaper 106. If the wireless communicationis used at the connection portion 304 in this manner, a necessity ofinstalling a transmission line for transmitting the image data and aconnector at the connection portion 304 can be eliminated, andtherefore, space saving and improvement of weather resistance can berealized.

In the present exemplary embodiment, the imaging unit 302 and the cameraplatform 303 are assumed to be connectable to each other in a pluralityof different orientations. For example, the imaging unit 302 can bedetached from the camera platform 303 and attached again to the cameraplatform 303 after being rotated around an axis in a Z-axis direction ofa coordinate system 310 by 180 degrees. In such a configuration, theorientation of the imaging unit 302 can be easily changed.

In the present exemplary embodiment, the coupler 103 is formed into ashape, like examples illustrated in FIGS. 4A to 4D, so that, forexample, a degree of coupling between the couplers 103 and 104 isprevented from being largely changed even when a change is made to theorientation in the case where the orientation of the coupler 104 ischangeable relative to the coupler 103 in this manner. FIGS. 4A to 4Deach illustrate the shape when the coupler 103 is viewed from the Z-axisdirection of the coordinate system 310.

In FIG. 4A, the coupler 103 includes an outer electrode 401 and an innerelectrode 402. The outer electrode 401 is disposed so as to surround theinner electrode 402. More specifically, the outer electrode 401 includesa bored portion, and the inner electrode 402 is located inside thisbored portion so as not to contact the outer electrode 401. The outerelectrode 401 includes a nearly point-symmetric shape (a rectangularshape) as viewed from the Z-axis direction perpendicular to a surface ofthe electrode 401. In such a configuration, the degree of couplingbetween the couplers 103 and 104 can be kept nearly constant.Consequently, stable communication can be established between thecouplers 103 and 104 even when the orientation of the coupler 103 ischangeable relative to the coupler 104 around an axis passing through anearly central point of the bored portion and extending nearly inparallel with the Z-axis direction.

The orientation of the coupler 103 relative to the coupler 104 is notlimited to the case where inversion by 180 degrees is possible. Theorientation of the coupler 103 can be changeable to differentorientations rotated by 60 degrees or 120 degrees. In such a case, thestable communication can be realized by forming an outer electrode 403into a nearly regular polygonal shape, as illustrated in FIG. 4B. Anouter electrode 405 can be formed into a nearly circular shape, asillustrated in FIG. 4C.

It is desirable to also form the inner electrode of the coupler 103 intothe nearly point-symmetric shape, as viewed from the Z-axis direction,and position the inner electrode of the coupler 103 around the center ofthe bored portion like the electrode 402 illustrated in FIG. 4A becausethis configuration can keep the degree of coupling between the couplers103 and 104 nearly constant. However, the configuration of the innerelectrode of the coupler 103 is not limited thereto. For example, aninner electrode 404 can be displaced from the center of the boredportion, as illustrated in FIG. 4B, in a case where the system 100 canenable the change the coupling degree to some extent. The rotationalaxis does not have to pass through a center of the electrode 403 as longas the rotational axis passes through an inside of the electrode 403. Ifa configuration in which an inner electrode 406 includes a bored portionis employed, as illustrated in FIG. 4D, a shaft member and a wired cablethat pass through the center of the coupler 103 can be installed in theconnection portion 304.

The coupler 104 can also have a shape like the examples illustrated inFIGS. 4A to 4D. The wireless communication based on the electromagneticfield coupling can be efficiently carried out by arranging the coupler104 in such a manner that the outer electrodes of the coupler 104 andthe coupler 103 at least partially overlap each other and the innerelectrodes of the coupler 104 and the coupler 103 at least partiallyoverlap each other, as viewed from the Z-axis direction. However, theshapes of the coupler 104 and the coupler 103 can be different from eachother.

A quality of the communication can be improved by keeping small adifference between the degree of coupling between the inner electrodesof the coupler 103 and the coupler 104 and the degree of couplingbetween the outer electrodes of the coupler 103 and the coupler 104. Tothis end, for example, it is desirable to arrange the dimension suchthat the outer electrode includes an area ten or more times an area ofthe inner electrode in a case where the coupler 103 and the coupler 104have similar shapes and the outer electrode and the inner electrode arelocated on the same plane. The communication quality can also beimproved by arranging the dimension such that the outer electrodeincludes an area twice or more the area of the inner electrode. In thepresent exemplary embodiment, the inner electrode and the outerelectrode are assumed to be located on the nearly same plane in each ofthe coupler 103 and the coupler 104, but are not limited thereto. Inother words, the positions of the inner electrode and the outerelectrode in the Z-axis direction can be different from each other.

The imaging unit 302 and the camera platform 303 are connectable to eachother at the connection portion 304 in the plurality of differentorientations in the above description, but the connection portion 304can include a mechanism that rotationally moves the imaging unit 302relative to the camera platform 303. For example, the connection portion304 can rotate the imaging unit 302 around the axis along the Z-axisdirection of the coordinate system 310 by rotating a member connectingthe imaging unit 302 and the camera platform 303 with use of a motor. Ifthe wireless communication for the communication is used at theconnection portion 304 configured to be rotationally movable in thismanner, the network camera 300 can, for example, prevent or reducedeterioration over time due to wear, and speed up a data transmissionrate compared to carrying out the communication using, for example, aslip ring which is an existing technique, at the connection portion 304.

In the case where the movement control is performed to rotate theimaging unit 302 relative to the camera platform 303, the coupler 103included in the imaging unit 302 is rotationally moved relative to thecoupler 104 included in the camera platform 303. In such a case, thechange in the degree of coupling between the coupler 103 and the coupler104 owing to the rotational movement can be additionally reduced byforming the electrode 405 included in the coupler 103 into the nearlycircular shape, as illustrated in FIGS. 4C and 4D. As a result, thenetwork camera 300 can reduce an increase or decrease in an amplitudeand reversal of a polarity of the electric signal received by thecoupler 104, so that stable data communication can be continued evenduring the rotational movement.

In this case, it is desirable that the rotational axis is an axispassing through a nearly central point of a bored portion of theelectrode 405 and extending nearly in parallel with the Z-axis directionso that the stability of the communication is improved. In addition, thestability of the communication can also be improved by also forming theinner electrode of the coupler 103 into a nearly circular shape like theelectrode 404 and the electrode 406. However, the shape of the electrodeof the coupler 103 used for this purpose does not necessarily need to bethe circular shape, and the coupler 103, shaped as illustrated in FIGS.4A and 4B, can be used in the case where, for example, the system 100can enable the change in the degree of coupling to some extent.

[Coexistence with Wireless Power Transmission]

The configuration using the wireless communication for the datacommunication at the connection portion 304 of the network camera 300has been described above. In addition, the wireless communication can beused also for power transmission at the connection portion 304, alongwith the data communication. Since the wireless power transmissioneliminates a necessity of installing a cable for transmitting power tothe connection portion 304, convenience is increased.

FIG. 5 illustrates an example in which the system 100 carrying out thewireless power transmission in addition to the wireless communication isapplied to a network camera 600. The same reference numerals as those inFIG. 3 are assigned to similar components in FIG. 5. The network camera600 includes a power line 603, a direct-current (DC)/alternating-current(AC) conversion circuit 604 (hereinafter referred to as a conversioncircuit 604), a power transmission antenna 605, a power receptionantenna 606, and a rectification circuit 607, in addition to theconfiguration of the network camera 300 illustrated in FIG. 3.

The wireless power transmission based on the electromagnetic fieldcoupling is carried out between the power transmission antenna 605 andthe power reception antenna 606. It is desirable to carry out thewireless power transmission based on the magnetic field coupling, suchas the electromagnetic induction method and the magnetic field resonancemethod to prevent or reduce interference of an electromagnetic fieldgenerated for the wireless power transmission, with the wirelesscommunication based on the electric field coupling between the coupler103 and the coupler 104. Therefore, in the present exemplary embodiment,the network camera 600 will be described referring to an example inwhich the power transmission antenna 605 and the power reception antenna606 are each a coiled conductor and the wireless power transmission iscarried out based on the magnetic field coupling. However, the wirelesspower transmission is not limited thereto, and can be carried out basedon the electric field coupling with, for example, the power transmissionantenna 605 and the power reception antenna 606 functioning as theelectrodes.

The power line 603 supplies DC (direct-current) power to the conversioncircuit 604. The conversion circuit 604 converts the supplied power intoAC (alternating-current) power, and inputs the converted AC power to thepower transmission antenna 605. The AC power input to the powertransmission antenna 605 is transmitted to the power reception antenna606 using the magnetic field coupling. The power reception antenna 606supplies the received AC power to the rectification circuit 607. Therectification circuit 607 then converts the supplied AC power into DCpower, and supplies the converted DC power to a functional unit (forexample, the imaging control unit 305) in the network camera 600. Inthis manner, the network camera 600 controls the wireless powertransmission between the power transmission antenna 605 and the powerreception antenna 606 using the conversion circuit 604 and therectification circuit 607.

FIG. 6 illustrates detailed configurations of the coupler 103, thecoupler 104, the power transmission antenna 605, and the power receptionantenna 606 at the connection portion 304 illustrated in FIG. 5. Asviewed from the Z-axis direction of the coordinate system 310, thecoupler 103 is located inside a loop formed by the power receptionantenna 606, and the coupler 104 is located inside a loop formed by thepower transmission antenna 605. If the network camera 600 is configuredin this manner, a positional relationship between the power transmissionantenna 605 and the power reception antenna 606 is prevented from beinglargely changed even when the imaging unit 302 is rotated, so thatstability of the power transmission can be improved. The stability ofthe power transmission can also be improved by concentricallypositioning the power transmission antenna 605 and the coupler 104 andconcentrically positioning the power reception antenna 606 and thecoupler 103.

When the power is input to the power transmission antenna 605, amagnetic flux 701 is generated at the connection portion 304, and thepower reception antenna 606 receives the power via this magnetic flux701. In the case where the coupler 103 is shaped as illustrated in FIGS.4A to 4D, it is conceivable that the magnetic flux 701 penetratesthrough a closed-loop electrode, like the electrode 401, the electrode403, the electrode 405, and the electrode 406, so that an inducedelectromotive force is generated at the coupler 103. Therefore, theelectrode of the coupler 103 can be formed into a shape having a slit,as illustrated in FIGS. 7A to 7D, to reduce such an inducedelectromotive force that can become noise.

FIGS. 7A to 7D illustrate shapes of the coupler 103 illustrated in FIGS.4A to 4D with slits added thereto, respectively. For example, anelectrode 801 illustrated in FIG. 7A includes a shape of the electrode401 illustrated in FIG. 4A with a slit added thereto, and a slitconnecting an outside of the electrode 801 and an inside of theelectrode 801, which is provided with a bored portion. If the electrodeof the coupler 103 is provided with such a slit, the inducedelectromotive force generated at the coupler 103 due to the magneticflux 701 is reduced, so that occurrence of the noise in the wirelesscommunication between the coupler 103 and the coupler 104 is preventedand thus the stability of the communication can be improved. In a casewhere an inner electrode 806 of the coupler 103 also has a boredportion, as illustrated in FIG. 7D, the stability of the communicationcan be improved by forming the inner electrode 806 into a shapeincluding a slit.

In a case where the coupler 104 is also formed into the shape includingthe slit similarly to the coupler 103, the degree coupling between thecouplers 103 and 104 varies based on the change in the orientation ofthe coupler 103 relative to the coupler 104. Therefore, it is desirableto set a width of the slit to be narrow enough to prevent the variationof the coupling degree from exceeding an allowable predeterminedthreshold value in the system 100.

[Exemplary Modification]

In the following description, an exemplary modification of theabove-described system 100 will be described. FIG. 8 illustrates aconfiguration example in a case where a balun 902 for changing anelectric signal input from a signal source 901 to the coupler 103 isadded to the power transmission side (a left side of the coupler 103) inthe system 100 illustrated in FIG. 1. The coupler 103 is similar to theconfiguration in the case of FIG. 1. A signal line 903 transmits thedifferential signal similarly to the signal line 102 illustrated in FIG.1.

The balun 902 is added, which is a point different from theconfiguration of FIG. 1, in that the signal source 901 and the coupler103 can be isolated from each other. In other words, a referencepotential can be changed between a side where the signal source 901 islocated and the other side where the coupler 103 is located, which areseparated by the balun 902 serving as a boundary therebetween. As aresult, the present exemplary modification can prevent or reducedeterioration of the communication quality due to a mismatch of thecoupling between the inner electrodes of the coupler 103 and the coupler104, and the coupling degree between the outer electrodes of the coupler103 and the coupler 104. The output of the electric signal from thesignal source 901 is not limited to the differential output, and canalso be a single-ended (single-phase) output. Even in the case where thesignal source 901 provides the single-ended output, the effect of thebalun 902 leads to the differential signal flowing through the signalline 903 and, the coupler 103 and the coupler 104 transmit and receivethe differential signal.

In FIG. 8, the balun 902 is a Sorta-Balun, but the configuration of thebalun 902 is not limited thereto. A similar effect can also be acquiredby employing a method that isolates the signal source 901 and thecoupler 103 from each other using a transformer instead of the balun902.

As described above with respect to FIGS. 3 and 6, the system 100 focuseson the example in which the shape of the coupler 103 and the shape ofthe coupler 104 are similar to each other, but the shape of the coupler103 and the shape of the coupler 104 are not limited thereto and can bedifferent from each other. For example, the change in the couplingdegree between the outer electrodes based on the rotational movement ofthe coupler 103 relative to the coupler 104 can also be kept small evenwhen the outer electrode of the coupler 103 is formed into the nearlycircular shape and the outer electrode of the coupler 104 is formed intoan arc shape as illustrated in FIG. 9. Further, similarly, as long asone of the inner electrode of the coupler 103 and the inner electrode ofthe coupler 104 include the nearly point-symmetric shape, the change inthe coupling based on the change in the orientation can be kept smalleven if the other inner electrode is not nearly point-symmetric.

A similar effect can be acquired even when the shape of the coupler 103and the shape of the coupler 104 are exchanged. More specifically, inFIG. 9, the differential signal can be input from the signal line 105 tothe coupler 104 and the differential signal received by the coupler 103can be output via the signal line 102. In this case, the shaper 106 isconnected to the signal line 102, and the signal source 101 is connectedto the signal line 105.

In the present exemplary embodiment, the system 100 is describedreferring to the example in which the differential signal isuni-directionally transmitted from the coupler 103 to the coupler 104.By carrying out the communication using the differential signal, aninfluence of external noise in the wireless communication can be reducedcompared with a case of carrying out single-ended transmission. However,how the communication is carried out is not limited thereto, and thecoupler 103 shaped as described in the present exemplary embodiment canalso be applied to bidirectional communication.

For example, a first electric signal can be input from the signal line102-1 to the inner electrode of the coupler 103, and a second electricsignal can be input from the signal line 105-2 to the outer electrode ofthe coupler 104. Then, an electric signal received by the innerelectrode of the coupler 104 based on the input of the first electricsignal can be output to the signal line 105-1, and an electric signalreceived by the outer electrode of the coupler 103 according to theinput of the second electric signal can be output to the signal line102-2. In this case, both the signal source 101 and the shaper 106 areconnected to each of the signal line 102 and the signal line 105.

Even in such a case, by using the coupler 103 shaped as described above,the stability of the communication can be improved in the case where theorientation of the coupler 103 relative to the coupler 104 ischangeable. Conversely, the first electric signal can be transmittedfrom the outer electrode of the coupler 103 to the outer electrode ofthe coupler 104, and the second electric signal can be transmitted fromthe inner electrode of the coupler 104 to the inner electrode of thecoupler 103. Two-channel unidirectional baseband communication can becarried out by inputting independent electric signals regarding datapieces different from each other to the inner electrode and the outerelectrode of the coupler 103.

The signal line, which is perpendicularly connected to the surface ofthe coupler, is illustrated in FIGS. 3, 5, 6, and 9, but the way thatthey are connected is not limited thereto. For example, the signal line102 can be a micro-strip line existing on the substrate where thecoupler 103 is formed. The system 100 has been described above focusingon the example in which the coupler 103 is rotationally moved, but thecoupler 104 can be rotationally moved or both the coupler 103 and thecoupler 104 can be rotationally moved.

The system 100 has been described above, with reference to FIGS. 3 and5, referring to the example in which the system 100 is employed for thepurpose of wireless communication performed by the network camera.However, the system 100 can also be applied to other uses. For example,the system 100 can be applied to an articulation portion of a robot armin factory automation (FA), a rotatable display, and a communicationcable for a mobile device supporting reversed insertion.

As described above, the system 100 according to the present exemplaryembodiment includes a first antenna configured to carry out wirelesscommunication based on electromagnetic field coupling between the firstantenna and a second antenna. The second antenna can change anorientation relative to the first antenna around a predetermined axis.The first antenna includes a first electrode including a bored portionconfigured such that this axis passes through the inside of the boredportion. The first antenna includes a second electrode located insidethis bored portion as viewed from a reference direction that is inparallel with this axis. The second antenna includes a third electrodeconfigured such that an electric signal is transmitted between the firstelectrode and the third electrode, and a fourth electrode configuredsuch that an electric signal is transmitted between the second electrodeand the fourth electrode. Such a configuration can improve the stabilityof the communication in a system configured to carry out wirelesscommunication based on electromagnetic field coupling between oneantenna including a plurality of electrodes and the other antenna whichorientation relative to this antenna is changeable.

According to the above-described exemplary embodiment, the stability ofthe communication can be improved in the system configured to carry outthe wireless communication between the one antenna including theplurality of electrodes and the other antenna which orientation relativeto this antenna is changeable.

Other Embodiments

Embodiment(s) can also be realized by a computer of a system orapparatus that reads out and executes computer executable instructions(e.g., one or more programs) recorded on a storage medium (which mayalso be referred to more fully as a ‘non-transitory computer-readablestorage medium’) to perform the functions of one or more of theabove-described embodiment(s) and/or that includes one or more circuits(e.g., application specific integrated circuit (ASIC)) for performingthe functions of one or more of the above-described embodiment(s), andby a method performed by the computer of the system or apparatus by, forexample, reading out and executing the computer executable instructionsfrom the storage medium to perform the functions of one or more of theabove-described embodiment(s) and/or controlling the one or morecircuits to perform the functions of one or more of the above-describedembodiment(s). The computer may comprise one or more processors (e.g.,central processing unit (CPU), micro processing unit (MPU)) and mayinclude a network of separate computers or separate processors to readout and execute the computer executable instructions. The computerexecutable instructions may be provided to the computer, for example,from a network or the storage medium. The storage medium may include,for example, one or more of a hard disk, a random-access memory (RAM), aread only memory (ROM), a storage of distributed computing systems, anoptical disk (such as a compact disc (CD), digital versatile disc (DVD),or Blu-ray Disc (BD)™), a flash memory device, a memory card, and thelike.

While exemplary embodiments have been described, it is to be understoodthat the invention is not limited to the disclosed exemplaryembodiments. The scope of the following claims is to be accorded thebroadest interpretation so as to encompass all such modifications andequivalent structures and functions.

This application claims the benefit of Japanese Patent Application No.2017-002713, filed Jan. 11, 2017, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A wireless communication system comprising: afirst antenna; a second antenna with an orientation relative to thefirst antenna that is changeable around a predetermined axis; and acommunication control unit configured to control wireless communicationbased on electric field coupling between the first antenna and thesecond antenna, wherein the first antenna includes a first electrodeincluding a bored portion, which is configured such that thepredetermined axis passes through an inside of the bored portion, and asecond electrode located inside the bored portion as viewed from areference direction that is in parallel with the predetermined axis, andwherein the second antenna includes a third electrode configured suchthat an electric signal is transmitted between the first electrode andthe third electrode, and a fourth electrode configured such that anelectric signal is transmitted between the second electrode and thefourth electrode.
 2. The wireless communication system according toclaim 1, further comprising a movement control unit configured torotationally move one or more of the first antenna and the secondantenna around the predetermined axis.
 3. The wireless communicationsystem according to claim 1, wherein the first electrode includes anearly point-symmetric shape around the predetermined axis as viewedfrom the reference direction.
 4. The wireless communication systemaccording to claim 1, wherein the first electrode includes anapproximately circular shape.
 5. The wireless communication systemaccording to claim 1, wherein the second electrode includes a boredportion.
 6. The wireless communication system according to claim 1,wherein the third electrode at least partially overlaps with the firstelectrode as viewed from the reference direction, wherein the fourthelectrode at least partially overlaps with the second electrode asviewed from the reference direction, and wherein at one or more of thesecond electrode and the fourth electrode include a nearlypoint-symmetric shape around the predetermined axis as viewed from thereference direction.
 7. The wireless communication system according toclaim 1, further comprising a balun or a transformer configured tochange an electric signal input from the communication control unit tothe first antenna.
 8. The wireless communication system according toclaim 1, wherein the communication control unit inputs an electricsignal to the first electrode, inputs an electric signal of oppositephase to the electric signal into the second electrode, and outputs anelectric signal based on an electric signal received by the thirdelectrode and an electric signal received by the fourth electrode. 9.The wireless communication system according to claim 1, wherein thecommunication control unit inputs an electric signal to the thirdelectrode, inputs an electric signal of opposite phase to the electricsignal into the fourth electrode, and outputs an electric signal basedon an electric signal received by the first electrode and an electricsignal received by the second electrode.
 10. The wireless communicationsystem according to claim 1, wherein the communication control unitinputs an electric signal to the first electrode, inputs an electricsignal to the fourth electrode, outputs an electric signal received bythe third electrode, and outputs an electric signal received by thesecond electrode.
 11. The wireless communication system according toclaim 1, further comprising: a third antenna; and a fourth antennaconfigured to carry out wireless power transmission between the thirdantenna and the fourth antenna, wherein the first antenna is locatedinside a loop formed by the third antenna as viewed from the referencedirection, and wherein the second antenna is located inside a loopformed by the fourth antenna as viewed from the reference direction. 12.The wireless communication system according to claim 1, wherein thefirst electrode includes a slit connecting an outside of the firstelectrode and the bored portion of the first electrode.
 13. The wirelesscommunication system according to claim 12, wherein the second electrodeincludes a slit connecting an outside of the second electrode and abored portion of the second electrode.
 14. The wireless communicationsystem according to claim 1, wherein the first antenna is included in afirst portion of an imaging apparatus, wherein the second antenna isincluded in a second portion of the imaging apparatus, which isconfigured to move rotationally around the predetermined axis relativeto the first portion, and wherein the communication control unitcontrols communication of image data based on imaging by the imagingapparatus, between the first antenna and the second antenna.
 15. Acommunication apparatus comprising: a first antenna with an orientationrelative to a second antenna included in another communication apparatusthat is changeable around a predetermined axis; and a communicationcontrol unit configured to control wireless communication based onelectric field coupling between the first antenna and the secondantenna, wherein the first antenna includes a first electrode includinga bored portion, which is configured such that the predetermined axispasses through an inside of the bored portion, and a second electrodelocated inside the bored portion as viewed from a reference directionthat is in parallel with the predetermined axis.
 16. The communicationapparatus according to claim 15, wherein the first electrode includes aslit connecting an outside of the first electrode and the bored portionof the first electrode.
 17. The communication apparatus according toclaim 16, further comprising a third antenna configured to carry outwireless power transmission between the third antenna and a fourthantenna included in the another communication apparatus, wherein thefirst antenna is located inside a loop formed by the third antenna asviewed from the reference direction.
 18. A communication method forcarrying out wireless communication between a first antenna and a secondantenna, the communication method comprising: controlling rotationalmovement of one or more of the first antenna and the second antennaaround a predetermined axis; and controlling wireless communicationbased on electric field coupling between the first antenna and thesecond antenna, wherein the first antenna includes a first electrodeincluding a bored portion, which is configured such that thepredetermined axis passes through an inside of the bored portion, and asecond electrode located inside the bored portion as viewed from areference direction that is in parallel with the predetermined axis, andwherein the second antenna includes a third electrode configured suchthat an electric signal is transmitted between the first electrode andthe third electrode, and a fourth electrode configured such that anelectric signal is transmitted between the second electrode and thefourth electrode.
 19. The communication method according to claim 18,further comprising controlling wireless power transmission between athird antenna and a fourth antenna, wherein the first antenna is locatedinside a loop formed by the third antenna as viewed from the referencedirection, and wherein the second antenna is located inside a loopformed by the fourth antenna as viewed from the reference direction. 20.The communication method according to claim 18, further comprisingtransmitting a first electric signal from the first electrode to thethird electrode and transmitting a second electric signal of oppositephase to the first electric signal from the second electrode to thefourth electrode.